PHOLADIDJS. 



59 



This shell is easily distinguished from P. cost4ta by the hinge-plates, which are cellular 

 beneath ; the two dorsal valves are lanceolate and placed side by side, which is characteristic 

 of the genus. It is living on the coast of South-Carolina, Georgia, and Florida, and is 

 quite common. 



Plate IX. Fig. 2, Natural size; side view. 



Locality. Simmons'. Museum, College of Charleston; Cabinet F. S. H. 



Genus, MARTESIA.— Leach. 



M A E T E S I A CUNEIFORM IS. 



Plate IX. Fig. 3. 



Pholas cuneifonnis, Say, Jour. Acad. Nat. Sci., Vol. 2, p. 322. 



Pholas cuneifonnis, Ravenel, Cat. Coll. Shells, p. 2. 



Pholas cuneiformis, L. R. Gibbes, Tuomey's Geol. So. Ca., appendix, p. xxii. 



Pholas cuneiformis, Be Kay, Zool. New- York, Art. Moliusca, p. 248. 



Pholas cuneiformis, Say's Conch. U. S., (Binney,) p. 108. 



Martesia cuneiformis, Adams, Gen. Recent Moliusca, Vol. 2, p. 331. 



Description. Shell sub-cuneiform; anterior margin nearly closed, transversely 

 truncated from the hinge ; the surface transversely striated in an undulated manner, with 

 elevated, minutely crenate lines; the intestitial lines smooth; these lines partially 

 interrupt a profoundly impressed longitudinal sulcus which passes from the beak to near 

 the middle of the base ; the inferior portion of this margin is destitute of striee ; posterior 

 margin attenuated by nearly rectilinear edges to a rounded tip ; surface transversely 

 wrinkled; hinge callous, composed of the reflected margin which forms a cavity before, 

 and is destitute of cells ; dentiform process incurved, slender filliform ; hinge-plate ovate 

 triangular, with a short projecting angle on the interior middle, and sub-acute behind ; 

 within, disk slightly contracted by an elevated line corresponding with the external 

 sulcus. — Say. 



The dorsal valve in this genus is single. Common on the coast of South-Carolina, and 

 fossil in the Post-Pleiocene. 



Plate IX. Fig. 3, Natural size. 



Locality. Simmons'. Museum, College of Charleston; Cabinet F. S. H. 



